444 MR. H. N. MOSELEY ON THE STRUCTURE OF THE STYLASTERIM. 
dactylopore projections, so as to be covered by these as by a projecting lip; and in 
places the margins of the gastropores themselves are drawn out into scale-like lips, 
though these lips are nearly always fused with nariform projections of contiguous 
dactylopores. Gastropores are frequently to be seen occurring isolated and solitary 
on the branches. 
The ampullae are, in this genus, conspicuous bodies, since they appear as hemi- 
spherical projections from the surfaces of the branches of about the size of a mustard- 
seed. In vigorous specimens they are closely crowded together in masses on both 
sides of the branches and branchlets in various regions of the flabellum. The ampullae 
commence as small cavities in the surface layer of the coralliun of the branches, and 
gradually enlarging in accordance with the development of the ovum contained in each, 
project more and more, until those containing mature, or nearly mature, planulae 
appear as the conspicuous projections above described. A hemispherical cavity, 
excavated in the surface of the corallum, corresponds with each ripe ampulla, but the 
excavation is usually not deep enough to render the entire ampullar cavity spherical 
in form. The cavity has rather the form of a sphere with one side flattened somewhat. 
In accordance with the gradual expansion of the ampullar cavity, its outer wall, which 
is finely reticular in structure, becomes thinner and thinner until, no doubt, it at last 
breaks away entirely for the escape of the imprisoned planula. The empty hollows 
remaining after this process is complete are abundantly present on the surfaces of the 
branches, and are often to be seen remaining on the older regions of the main stems, 
although in these older regions there is a tendency to obliteration, by interstitial 
calcareous deposit, of all pores and ampullae. 
The mass of the corallum is composed, as in other St-ylasteridae, of hard calcareous 
tissue, permeated in all directions by meshworks of canals. The canals generally are, 
in the present genus, larger in proportion to the size of the zooids than in most other 
forms (Plate 37), and the meshworks formed by them are comparatively widely open. 
The main canals have a general tendency to traverse the axes of the stems and 
branches, spreading out at an inclination corresponding with that of the pore cavities 
towards the surfaces. This arrangement necessarily results from the mode of growth. 
In the older regions of the stem the corallum becomes more compact and stony by 
obliteration of many of the canals, but the main canals appear never to become 
entirely obliterated, even very low down towards the bases of the stems. 
Soft structures o/’Errina labiata. (Plate 37.) 
Coenosctrc. — The coenosarcal meshwork in Errina labiata is more widely open in its 
structure than in Sporadopora dichotoma (Plate 37). Hence the mass of soft structures 
separated from the corallum by decalcification is comparatively soft and less able to 
maintain the original form of the corallum. In the present species, however, in all the 
actively living branches it is not, as in Sporadopora dichotoma, a mere surface layer of 
